1. Field of the Invention
This invention relates to medical apparatus and more particularly to an apparatus for intermittently applying external compression to a portion of a body for therapeutic purposes, for example to prevent complications of the circulatory system such as pulmonary embolism.
2. Description of the Prior Art
One of the most serious complications which occurs after surgery has been pulmonary embolism. Although it is generally accepted that venous stasis in the lower extremities is the major factor in venous thrombosis and subsequent pulmonary embolism, such a condition is difficult to detect since clots in the veins of the legs and pelvis produce symptoms only when they become attached to the vein wall and the greatest danger of pulmonary embolism is already passed. Methods of prevention and treatment have included early ambulation, post-operative exercises in bed, use of anti-coagulants, the electrical stimulation of calf muscles during surgery and wrapping the legs during and after surgery.
However, one of the most successful methods of treatment has been the intermittent application of pressure to the legs. Collens et al Patent No. 2,140,898 entitled "Method of and Apparatus For Producing Intermittent Venous Occlusion" discloses a device for applying pressure to a leg to obstruct the venous flow for a relatively short period of time at a predetermined frequency. Although such devices produced the desired results, they required a source of electricity to power the timing means, electric motor and/or valves which controlled the air pressure for the pneumatic cuff or boot on the patient's leg. The introduction of such apparatus into the operating room required the units to be made explosion proof which greatly added to their weight, bulk and cost. These negative factors militated against general acceptance of intermittent compression devices